Option Strict On

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Imports System

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Public Module Program

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    Dim _numStudents As Integer

    Dim _studentIds As String()

    Dim _englishResults As Integer()

    Dim _mathsResults As Integer()

    Dim _scienceResults As Integer()

    Public Sub Main(args As String())

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        Dim quit = false

        Do

            DisplayMenu()

            Dim choice As String = Console.ReadLine()

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            If (choice = "q")

                quit = true

            ElseIf(choice="1")

                EnterResults()

            ElseIf(choice="2")

                DisplayResults()

            ElseIf(choice="3")

                StudentSearch()

            Else 

                Console.WriteLine("Invalid selection. Please try again.")

            End If

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            Console.WriteLine()

        Loop Until quit

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        Console.WriteLine("Bye!")

    End Sub

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    Private Sub DisplayMenu()

        Console.WriteLine("What would you like to do?")

        Console.WriteLine("1: Enter results")

        Console.WriteLine("2: Display results")

        Console.WriteLine("3: Search for a student's results")

        Console.WriteLine("q: Quit")

        Console.Write(">")

    End Sub

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    Private Sub EnterResults()

        Console.Write("How many students are there? ")

        Dim numStudentsText = Console.ReadLine()

        If (numStudentsText = "")

            return

        End If

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        Dim numStudents = Integer.Parse(numStudentsText)

        if (numStudents < 1)

            return

        End If

        _numStudents = numStudents

        ReDim _studentIds(numStudents-1)

        ReDim _englishResults(numStudents-1)

        ReDim _mathsResults(numStudents-1)

        ReDim _scienceResults(numStudents-1)

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        Console.WriteLine("Enter details for each student in the format: <ID>,<English Mark>,<Maths Mark>,<Science Mark>")

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        For i = 0 To numStudents-1

            Dim studentId = ""

            Dim englishMark As Integer

            Dim mathsMark As Integer

            Dim scienceMark As Integer

            Dim line As String

            Dim parts As String()

            Dim isValid as Boolean

            Do

                isValid = true ' Assume it's ok unless we find otherwise

                Console.Write("Student {0} of {1}: ", i+1, numStudents)

                line = Console.ReadLine()

                parts = line.Split(","C)

                If (parts.Length <> 4) Then

                    isValid = false

                Else

                    studentId = parts(0).Trim() 'Remove leading and trailing space

                    if (Not IsValidStudentId(studentId)) Then

                        isValid = false

                    End If

​

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                    englishMark = GetAdjustedMarkFromInputText(parts(1))

                    If (englishMark = -1) Then

                        isValid = false

                    End If

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                    mathsMark = GetAdjustedMarkFromInputText(parts(2))

                    If (mathsMark = -1) Then

                        isValid = false

                    End If

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                    scienceMark = GetAdjustedMarkFromInputText(parts(3))

                    If (scienceMark = -1) Then

                        isValid = false

                    End If

                End If

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                If Not isValid Then

                    Console.WriteLine("Invalid entry. Please try again.")

                End If

            Loop Until isValid

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            ' Store the results into the array

            _studentIds(i) = studentId

            _englishResults(i) = englishMark

            _mathsResults(i) = mathsMark

            _scienceResults(i) = scienceMark

​

        Next

​

    End Sub

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    Private Function IsValidStudentId(studentId As String) As Boolean

        If (studentId.Length <> 5) then

            Return False

        End If

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        ' Every character in the string must be a digit

        For i = 0 To studentId.Length-1

            If Not Char.IsDigit(studentId(i)) Then

                Return False

            End If

        Next

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        Return True

    End Function

​

    ''' <summary>

    ''' Attempts to read a mark from some text. If it is not a valid

    ''' mark (0-100) then -1 is returned; otherwise, the 'adjusted' mark

    ''' is returned (no less than 20).

    ''' </summary>

    Private Function GetAdjustedMarkFromInputText(text As String) As Integer

        Dim mark As Integer

        Dim isValidInteger = Integer.TryParse(text, mark)

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        If (isValidInteger AndAlso mark >=0 AndAlso mark <= 100)

            If (mark < 20)

                Return 20

            Else 

                Return mark

            End If

        Else 

            Return -1

        End If

​

    End Function

​

​

    Private Sub DisplayResults()

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        If _numStudents > 0 Then

            DisplayStudentTableHeader()

            For i = 0 To _numStudents-1

                DisplayStudentRow(i)

            Next

            DisplayTableDivider()

            Console.WriteLine()

            DisplayTableDivider()

            DisplayTableRow("", "English", "Maths", "Science")

            DisplayTableDivider()

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            DisplayTableResultsRow("Average", Average(_englishResults), Average(_mathsResults), Average(_scienceResults))

            DisplayTableResultsRow("Minimum", Minimum(_englishResults), Minimum(_mathsResults), Minimum(_scienceResults))

            DisplayTableResultsRow("Maximum", Maximum(_englishResults), Maximum(_mathsResults), Maximum(_scienceResults))

            DisplayTableDivider()

        Else 

            Console.WriteLine("There are no student records to display.")

        End If

    End Sub

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    Private Sub DisplayStudentRow(studentIndex As Integer)

        DisplayTableResultsRow(_studentIds(studentIndex), _englishResults(studentIndex), _mathsResults(studentIndex), _scienceResults(studentIndex))

    End Sub

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    Private Sub DisplayTableResultsRow(heading As String, englishResult As Integer, mathsResult As Integer, scienceResult As Integer)

        Console.WriteLine("|{0,-8}|{1,-8}|{2,-8}|{3,-8}|", heading, englishResult, mathsResult, scienceResult)

    End Sub

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    Private Sub DisplayTableRow(heading As String, col1 As String, col2 As String, col3 As String)

        Console.WriteLine("|{0,-8}|{1,-8}|{2,-8}|{3,-8}|", heading, col1, col2, col3)

    End Sub

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    Private Sub DisplayStudentTableHeader()

        DisplayTableDivider()

        DisplayTableRow("Student", "English", "Maths", "Science")

        DisplayTableDivider()

    End Sub

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    Private Sub DisplayTableDivider()

        Console.WriteLine("+--------+--------+--------+--------+")

    End Sub

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    Private Function Average(results As Integer()) As Integer

        Dim sum = 0

        Dim numResults = results.Length

        For i = 0 To numResults - 1

            sum = sum + results(i)            

        Next

        Return CInt(sum / numResults)

    End Function

​

    Private Function Minimum(results As Integer()) As Integer

        Dim min = 100

        Dim numResults = results.Length

        For i = 0 To numResults - 1

            If (results(i) < min)

                min = results(i)

            End If

        Next

        Return min

    End Function

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    Private Function Maximum(results As Integer()) As Integer

        Dim max = 0

        Dim numResults = results.Length

        For i = 0 To numResults - 1

            If (results(i) > max)

                max = results(i)

            End If

        Next

        Return max

    End Function

​

    Private Sub StudentSearch()

        If _numStudents > 0 Then

            Console.Write("Enter the student id: ")

            Dim searchId = Console.ReadLine().Trim()

            Dim found = false

            For i = 0 To _numStudents - 1

                If _studentIds(i) = searchId Then

                    DisplayStudent(i)

                    found = True

                End If

            Next

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            if Not found Then

                Console.WriteLine("Student not found.")

            End If

        Else 

            Console.WriteLine("There are no student records to search.")

        End If

    End Sub

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    Private Sub DisplayStudent(studentIndex As Integer)

        Dim results As Integer()

        Dim subjects As String()

        ReDim results(2)

        ReDim subjects(2)

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        results(0) = _englishResults(studentIndex)

        subjects(0) = "English"

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        results(1) = _mathsResults(studentIndex)

        subjects(1) = "Maths"

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        results(2) = _scienceResults(studentIndex)

        subjects(2) = "Science"

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        Dim min = Minimum(results)

        Dim minIndex = Array.IndexOf(results, min)

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        Dim max = Maximum(results)

        Dim maxIndex = Array.IndexOf(results, max)

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        ' Output the results

        DisplayStudentTableHeader()

        DisplayStudentRow(studentIndex)

        DisplayTableDivider()

        Console.WriteLine()

        Console.WriteLine("Average mark: {0}", Average(results))

        Console.WriteLine("Lowest mark was in {0}: {1}", subjects(minIndex), min)

        Console.WriteLine("Highest mark was in {0}: {1}", subjects(maxIndex), max)

​

    End Sub

End Module

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